The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Using energy-efficient circuits in a battery-powered portable electronic device increases a battery life and reduces a heat dissipation requirement of the portable electronic device. Class D amplifiers are energy-efficient amplifiers, and accordingly, the portable electronic device may use a class D amplifier to drive a load such as a speaker.
A class D amplifier operates by rapidly turning one or more switching devices, such as transistors, on and off, with the ratio of the on time to the off time (the duty cycle) being determined by an input signal of the class D amplifier. The switch may be controlled at a frequency much higher than the maximum frequency of the input signal. A low pass filter is connected to the output to of the class D amplifier to remove high frequency components of the output signal, leaving only the amplified input signal.
In a battery-powered device, a voltage boost power supply may be used to produce a boost voltage that remains constant even as the battery voltage changes due to the discharging or charging of the battery. The voltage boost power supply may also be used to supply a voltage higher than the voltage supplied by the battery.
An adaptive boost power supply changes the boost voltage according to a change in operating conditions. For example, an adaptive boost supply may provide a first voltage as a power supply of an amplifier when a power output of the amplifier is low, and a second voltage higher than the first voltage as the power supply of the amplifier when the power output of the amplifier is high. The adaptive boost power supply may determine whether to supply a high boost voltage or a low voltage using one or more input signals to the amplifier.